JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Laws of Motion

A body of mass 2 kg moving with velocity of

v_{in} = 3 \hat{i} + 4 \hat{j} ms^{- 1}

enters into a constant force field of 6 N directed along positive z-axis. If the body remains in the field for a period of

\frac{5}{3}

seconds, then velocity of the body when it emerges from force field is

Answer: (B)

Solution

The force

6 \hat{k} N

on the

2 kg

body produces an acceleration

a = \frac{6}{2} \hat{k} = 3 \hat{k} m s^{- 2}

along

z

alone. The in-plane velocity stays unchanged while the

z

-component grows as

a t = 3 \times \frac{5}{3} = 5 m s^{- 1}

. Using

v = u + a t

, the velocity on emerging from the field is

3 \hat{i} + 4 \hat{j} + 5 \hat{k} m s^{- 1}

JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Single correct option